This invention relates to sickle bar mowers of the agricultural or highway type and, more particularly, to a pitman mower having novel cutterbar control and mounting arrangements which coact to produce an inexpensive lightweight mower of relatively uncomplicated design without the sacrifice of the functional aspects necessary in a commercially acceptable mower, such as vibration isolation, cutterbar floatation and lift, breakback capability of the cutterbar in response to obstructions in the field, and durability.
Commercially mowers in use today comprise two general types, the balanced head or wobble drive mower and the pitman mower. Both types have their advantages and their deficiencies. The major deficiency of the wobble drive type is cost, the major difference being in the drive itself. On the other hand, this type of mower is relatively free from vibration. Simple pitman mowers are relatively inexpensive but suffer the vice of transmitting sickle vibration back to the tractor causing operator fatigue and premature failure of parts. Counterbalancing the sickle forces becomes complicated and expensive. Both systems provide linkages for raising the cutterbar to a gag position and for lifting the entire unit off the ground preferably including a floatation spring to reduce the pressure of the mower against the ground. Breakaway of the cutterbar in response to obstructions, such as tree stumps, is provided either by the cutterbar itself pivoting back about the drag bar which does not lend itself to pitman mowers or by having both the drag bar and the cutterbar pivot back as the unit, sometimes also including part of the frame.
In the referenced copending application, Ser. No. 566,879, there is claimed a unique vibration-inhibiting mower mounting system wherein the hitch frame of the mower and the drag bar are connected in a generally horizontal four bar linkage by a pair of fore-and-aft links wherein in one of the links is transversely resilient, preferably a leaf spring, having one end rigidly connected to the drag bar to maintain the lateral position of the mower. Of the prior art pertaining to this feature, the Schroeppel U.S. Pat. No. 2,495,986 and the Scarnato et al. U.S. Pat. No. 3,092,947 and U.S. Pat. No. 3,302,376 appear to be the most pertinent. A discussion of these references and other less pertinent references may be found by reference to the copending application.
In the referenced copending application, Ser. No. 566,877, a unique pull bar assembly is claimed which fulfills the combined functions of draft link, part of the lifting linkage, and breakaway link. More specifically, the pull bar assembly comprises a fore-and-aft link interconnecting the hitch frame of the mower with the drag bar which is rotatable about an axis generally longitudinal thereof, a floatation spring and lifting chain being connected to the pull bar assembly and disposed to rotate it against the load imposed thereon by a gag link connected thereto at a point away from the axis of rotation and extending to the cutterbar to control its rotation. The pull bar assembly is also longitudinally extendable in response to overload conditions on the cutterbar. Prior art references pertinent to this feature include the Hurlburt et al. U.S. Pat. No. 3,407,578 and U.S. Pat. No. 3,418,796 and the Burton U.S. Pat. No. 2,699,635 which are discussed in the copending application.
It is our belief that while either of the inventions claimed in the copending applications might be used advantageously independently of the other, their advantages are best utilized when combined in a single mower structure to produce an economical, relatively uncomplicated and durable pitman mower.
Moreover, the resulting mower possesses several advantages which would not be realized except when the inventions are combined as taught herein. For example, when the pull bar assembly is used, a certain amount of pivoting in a horizontal fore-and-aft plane occurs between the left end of drag bar and the hitch frame during the gagging operation. In the prior art design of the left end, a horizontal pivot mounting is provided at this point. However, by utilizing the leaf spring in combination with the pull bar assembly, this horizontal pivot mounting is unnecessary and can be eliminated since the leaf spring may be torsionally deflected enough to satisfy the movement of the drag bar relative to the hitch frame.
A further advantage of the combination is that the vibration-inhibiting action of the leaf spring is not dampened by external transverse forces imposed on the drag bar by the floatation and lifting members when the above-mentioned pull bar is used in conjunction therewith since both the floatation spring and lifting chain are vertically oriented especially in the operating position of the mower. Conventional lift linkages are generally not vertically oriented, although the spring in the Hurlburt U.S. Pat. No. 3,418,796 is, and thus exert transverse loads on the drag bar which would prestress the leaf spring and dampen its vibration-inhibiting properties.
A still further advantage of utilizing the above-mentioned pull bar in combination with the leaf spring is that in utilizing the four bar parallel linkage including a resilient link, rigidly mounted to the drag bar to inhibit vibration transfer from the sickle to the tractor, the fewer connections there are between the drag bar and the hitch frame while maintaining the necessary functions of the mower, the better. Since the pull bar combines the functions of draft link, lift linkage connection between the frame and drag bar, and breakaway link, only two connections to the vibrating part of the mower are necessary. In the prior art, where these three functions are not combined, additional connections are necessary.